Underdrive Pulleys

[Breakpopin]

Has anyone here underdrive their BMW's pulleys before? Curious to know what are the results like. Any pros and cons of this upgrade? I heard that it may cause the battery to have problems charging and temp overheating issues.. :blush:

 

[3er]

I'm using it for almost a year now.

Pros - better acceleration

Cons - none

Your concerns:
charging - none
overheating - none

 

[Breakpopin]

Ahhh Thanks for the swift response 3er.

Which brand of pulleys are you using currently? And which pulley does the set contains? Water Pump, aircond, alternator etc etc..

 

[DanPromote]

I've tested both undersized and lightened crankpully not on BMW but on Protons before. Nevertheless the results should be the same mechanically :-

1. Undersized pully - faster pickup but causes a lot of problems, car dies off suddenly during corners due to lack of battery power and fuel consumption is higher

2. Lightened pully but replica of original (same size as original) - has all the advantages of the undersized pully but none of the disadvantage as it is the same specs as the original pully, only thing is that it is made of Aluminium T7 material (the lightest grade and the toughest, same type of grade used for aircraft parts). Overall around 30% of the original weight only.

So if you have a chance, go for lightened pully but not undersized pully.

* Where was the undersized pully from? Suprisingly it is original from Proton! They used it for their export models and the car was driven for the past 7 years with this problem without knowing until it was taken out.

 

[Breakpopin]

hi Dan,

mmm so i guess there IS such a problem as the battery havin difficulties charging eh. You did mentioned having a higher fuel Consumption.. why is that?

On a different note, the undersized pulleys on your proton may be too undersized LOL, since its more like a product defect than a purposely manufactured undersized pulley hehe.

Lightened pulleys, anyone here has tried them on BMWs then? Any info on where to get them?

 

[Alvin]

Underdrive does not mean under size.
You should never use a smaller size pulley. There are 2 kind of after mkt pulleys aroung.

1. Lighten Pulley. There are 3 pulleys for this. Crank, Aircon & Alternator.
2. Larger diameter plus lighten crank pulley - The larger dia will reduce stress on the crank in rotation mass meaning less energy used to drive the other components.

I'm using a no 2 in my MCS. It drive the SC even faster & increase the voltage in the system. I'm reading about about 14amp on my volt meter especially on track.

Thk what i said is correct.

 

[Breakpopin]

Ah thanks Alvin for the enlightenment! now i have a better picture of these pulleys..

Calling Mr.Fabiannnnnnn!! Lol

 

[Zoggee]

h34r: huh..??? h34r:

 

[Breakpopin]

Originally posted by Zoggee@Mar 15 2006, 09:37 AM
h34r: huh..??? h34r:

h34r: what!? canot ar! u scared ah!

 

[Zoggee]

Originally posted by Breakpopin+Mar 15 2006, 07:09 PM-->QUOTE (Breakpopin @ Mar 15 2006, 07:09 PM)

 

[Breakpopin]

Originally posted by Zoggee+Mar 15 2006, 09:42 AM-->QUOTE (Zoggee @ Mar 15 2006, 09:42 AM)

Originally posted by Breakpopin@Mar 15 2006, 07:09 PM

 

[The Necessary]

Yes, the correct terminology for what you're looking for is Underdrive pulley, and not Undersized pulleys.

Underdrive pulley are larger than the "normal" pulleys, it's like the "big" gears on a bicycle- big = less effort to turn = less rotation/rounds also. These oversized, underdrive pulleys are used to underdrive/reduce the load on the engine by non critical components like aircon compressors, alternator, power steering pumps, etc.. Supposedly leading to more power for more important things like accelerating.

Converesely, what Alvin is talking about; substituting a smaller sized pulley on his Supercharger is like shifting to the smaller gear on your bicycle; leading to more effort to drive the component, but more rotation, and hence in a supercharger, great boost pressure, and more go.

 

[Breakpopin]

An thank you all for explaining.. at least now i know that an Underdrive pulley is not undersized and it also has nothing to do with Zoggee's Underwear.

DanPromote posted something on his undersized pulleys for his proton, which made me think that underdrive pulleys are smaller than the original pulleys LOL.

 

[The Necessary]

Oh, and any reputable manufacturer of Underdrive pulleys (they're really simple to make anyways!) will make sure they're pulleys are lighter than the OEM/stock ones. It's really nothing to shout about.

Please restrict all mention of Zoggee's underwear to the Autobahn, please, that is a very adult topic. Oh, and very gross too.

 

[Zoggee]

Originally posted by The Necessary@Mar 15 2006, 07:34 PM


Please restrict all mention of Zoggee's underwear to the Autobahn, please, that is a very adult topic. Oh, and very gross too.

NECC,
whatever lah......

Popo...


Dude....you want to shorthen the lifespan of ur engine??? sumore u running on slushbox.

You want Race car or daily car...??

 

[Breakpopin]

Originally posted by The Necessary@Mar 15 2006, 10:04 AM
Please restrict all mention of Zoggee's underwear to the Autobahn, please, that is a very adult topic. Oh, and very gross too.

Damn! And i thought its easy to write appropriately in forums. :rofl:

Anyway thanks Necc, will look into it, Fab told me he can find me some

Dude....you want to shorthen the lifespan of ur engine???

NO wonder not talking to me in MSN, u so busy hantaming me in this thread! KNN
h34r:

 

[The Necessary]

Zoggee,

don't scare him la, underdrive pulleys will not shorten the lifespan of an engine. That's like saying that driving with the air con on is better for the engine than driving with it off.

 

[Zoggee]

Originally posted by The Necessary@Mar 15 2006, 07:40 PM
Zoggee,

don't scare him la, underdrive pulleys will not shorten the lifespan of an engine. That's like saying that driving with the air con on is better for the engine than driving with it off.

haha... :rofl:

ssshhhh...trying to make his brain works ma.. h34r:

keep asking me all sought of stuff on MSN... :aggressive:

 

[Breakpopin]

Haiz, speaking of Shortening the lifespan of the engine... My engine died on me after 2 weeks of transplant ok.. @_@ What is there to be scared of anymore?? BMWs are meant to go into the workshop LOL

ssshhhh...trying to make his brain works ma.. ph34r.gif

keep asking me all sought of stuff on MSN... aggressive.gif

KNN!! :hmmph:

 

[fabianyee]

actually underdrive pulley is smaller in diameter.

Visualize the front ring gears on the bicycle. the bigger the ring gear, the more effort u need to pedal it. the smaller the front ring gear the lesseffort required to pedal.

Smaller pulley on the crank means smaller circumferrence, hence less belt travel for every revolution, hence 'underdriving' the alternator, powersteering pump, fan clutch and waterpump.

As for the case of the bigger pulley on the MCS, it's to increase the boost on the supercharger. There are 2 ways of doing that. one is bigger crank pulley, the other is smaller supercharger pulley.